The 117th CBC in the West Indies and Bermuda

There were 26 Christmas Bird Counts in the region this season; Bermuda, seven from the Bahamas, two in the Dominican Republic, one from Haiti, five from Puerto Rico, three from the US Virgin Islands and two from the British Virgin Islands. Cuba returned with four counts. The Barbados count has been revived after a very long hiatus; and Andros, Bahamas has returned with great enthusiasm enjoined by the Bahamas National Trust. High species count honors go to Fajardo, Puerto Rico with 127 species and the highest observer participation (70) followed by Cabo Rojo, Puerto Rico (124 species) with 64 birders counting birds. 

Native ducks and grebes:  Four counts provided a total of 50 West Indian Whistling-Ducks and Barbados listed 90 Black-bellied Whistling-Ducks, a probable source of expansion through the Antilles. White-cheeked Pintails (820) were counted at 12 circles. Ruddy Ducks (31) were found on three counts which is fewer than last season. Least Grebes (30) perhaps decreasing this year in the region were found on only four of the 26 counts submitted this year.

Landbirds and introduced species:  The most commonly reported land bird was Common Ground-Dove seen on 25 of 26 counts. Northern Mockingbird seen on 22 of 26 counts.  Neotropical migrant warblers in the Antilles were led this year by American Redstart observed on 18/26 circles with 238 individuals followed by Prairie Warbler 17/26 and 248 total then Northern Parula 16/26 and 192 total birds. Twenty migrant warbler species were reported in the Antilles including a Swainson’s. The highest count for a migrant warbler was 534 (Palm Warbler) followed by Northern Waterthrush (345). Bermuda consistently records the greatest number of warbler species for a given circle (19 this year) nearly matching the region’s total. Resident warbler species were not included in the analysis.

The highest percentage (relative abundance) for an introduced species was 58% (15/26) for House Sparrow outpacing Eurasian Collared-Dove at 42%. This “urban” dove appears to be holding on yet not dramatically depressing numbers of native ground-foraging columbids which can occupy forest openings (Figures 1a-d, 2a-d). Graphs derived from NAS database.

From left to right: Eurasian Collared-Dove and Common Ground-Dove Photo: Robert L. Norton
From left to right: Zenaida Dove and White-winged Dove Photo: Robert L. Norton

Figures 1. a-d. Comparison of native ground-feeding columbids vs an introduced columbid over a ten-year CBC period in the Bahamas.

While the trends in the Bahamas seem to indicate Eurasian Collared-Dove (EUCD) seems to be declining of late, looking closely at years 2012-2014 when EUCD numbers were peaking, native species numbers, though a fraction of peak collared-dove population per/party hrs, were showing signs of stress, particularly Zenaida Dove. Whether this is displacement in urban environments or throughout is not clear.

In Puerto Rico the situation is different.  Eurasian Collared-Dove numbers per party hour are much lower than native species populations (Figs 2a-d.). Comparing decadal trends, EUCD seems to be steadily increasing while Common Ground-Dove numbers are holding or dropping slightly and other native columbids are holding their own or increasing.

From left to right: Eurasian Collarded-Dove and Common Ground-Dove Photo: Robert L, Norton
From left to right: Zenaida Dove and White-winged Dove Photo: Robert L. Norton

Figures 2a-d. Comparison of ground-feeding native columbids vs an introduced columbid over a ten-year CBC period in Puerto Rico.

These dynamics suggest that EUCD may not be having a dramatic effect on native ground-feeding columbids in the northern Antilles. Comparing EUCD trends against Scaly-naped, White-crowned and Plain pigeons would seem problematic as their feeding habits are different; ground-feeding versus arboreal in forests for the others. 

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